Ecdsa

Fix the PyPI wheel - the old version included .pyc files.

Fix the argument order for Curve constructor (put openssl_name= at the end,
with a default value) to unbreak compatibility with external callers who used
the 0.11 convention.

Switch to Versioneer for version-string management (fixing the broken
`ecdsa.__version__` attribute). Add Curve.openssl_name property. Mention
secp256k1 in README, test against OpenSSL. Produce "wheel" distributions. Add
py3.4 and pypy3 compatibility testing. Other minor fixes.

Add signature-encoding functions "sigencode_{strings,string,der}_canonize"
which canonicalize the S value (using the smaller of the two possible
values). Add "validate_point=" argument to VerifyingKey.from_string()
constructor (defaults to True) which can be used to disable time-consuming
point validation when importing a pre-validated verifying key. Drop python2.5
support (untested but not explicitly broken yet), update trove classifiers.

Make the secp256k1 available in __init__.py too (thanks to Scott Bannert).

Add secp256k1 curve (thanks to Benjamin Dauvergne). Add deterministic (no
entropy needed) signatures (thanks to slush). Added py3.2/py3.3 compatibility
(thanks to Elizabeth Myers).